We measured AlGaN/GaN heterostructure using scanning nonlinear dielectric microscopy (SNDM) [1], which can measure both carrier and polarization profile in AlGaN/GaN heterostructure. As a result, GaN spontaneous polarization and AlGaN polarization which is sum of spontaneous polarization and piezoelectric polarization were clearly distinguished. Two dimensional electron gas (2DEG) was observed at the AlGaN/GaN interface. This results show that SNDM is useful method for evaluation of 2DEG profile and polarization profile in AlGaN/GaN heterostructure.